Medical sensor and technique for using the same

ABSTRACT

A sensor assembly is provided that includes a frame having two or more structural supports. A coating is provided over the frame. The coating has at least one deformable region disposed between the two or more structural supports. As least one optical component is disposed within the at least one deformable region such that the at least one optical component can move relative to the two or more structural supports. A biasing component is attached to an end of the frame such that at least two different portions of the coated frame are biased closed in the absence of a sufficient opening force. The sensor may be placed on a patient&#39;s finger, toe, ear, and so forth to obtain pulse oximetry or other physiological measurements. A skeletal frame and a method for manufacturing a skeletal framework are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/199,524 filed Aug. 8, 2005, the disclosure of which is herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to medical devices and, moreparticularly, to sensors used for sensing physiological parameters of apatient.

2. Description of the Related Art

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

In the field of medicine, doctors often desire to monitor certainphysiological characteristics of their patients. Accordingly, a widevariety of devices have been developed for monitoring physiologicalcharacteristics. Such devices provide doctors and other healthcarepersonnel with the information they need to provide the best possiblehealthcare for their patients. As a result, such monitoring devices havebecome an indispensable part of modern medicine.

One technique for monitoring certain physiological characteristics of apatient is commonly referred to as pulse oximetry, and the devices builtbased upon pulse oximetry techniques are commonly referred to as pulseoximeters. Pulse oximetry may be used to measure various blood flowcharacteristics, such as the blood-oxygen saturation of hemoglobin inarterial blood, the volume of individual blood pulsations supplying thetissue, and/or the rate of blood pulsations corresponding to eachheartbeat of a patient.

Pulse oximeters typically utilize a non-invasive sensor that is placedon or against a patient's tissue that is well perfused with blood, suchas a patient's finger, toe, forehead or earlobe. The pulse oximetersensor emits light and photoelectrically senses the absorption and/orscattering of the light after passage through the perfused tissue. Thedata collected by the sensor may then be used to calculate one or moreof the above physiological characteristics based upon the absorption orscattering of the light. More specifically, the emitted light istypically selected to be of one or more wavelengths that are absorbed orscattered in an amount related to the presence of oxygenated versusde-oxygenated hemoglobin in the blood. The amount of light absorbedand/or scattered may then be used to estimate the amount of the oxygenin the tissue using various algorithms.

In many instances, it may be desirable to employ, for cost and/orconvenience, a pulse oximeter sensor that is reusable. Such reusablesensors, however, may be uncomfortable for the patient for variousreasons. For example, the materials used in their construction may notbe adequately compliant or supple or the structural features may includeangles or edges.

Furthermore, the reusable sensor should fit snugly enough thatincidental patient motion will not dislodge or move the sensor, yet notso tight that it may interfere with pulse oximetry measurements. Such aconforming fit may be difficult to achieve over a range of patientphysiologies without adjustment or excessive attention on the part ofmedical personnel. In addition, lack of a tight or secure fit may allowlight from the environment to reach the photodetecting elements of thesensor. Such environmental light is not related to a physiologicalcharacteristic of the patient and may, therefore, introduce error intothe measurements derived using data obtained with the sensor.

Reusable pulse oximeter sensors are also used repeatedly and, typically,on more than one patient. Therefore, over the life of the sensor,detritus and other bio-debris (sloughed off skin cells, dried fluids,dirt, and so forth) may accumulate on the surface of the sensor or increvices and cavities of the sensor, after repeated uses. As a result,it may be desirable to quickly and/or routinely clean the sensor in athorough manner. However, in sensors having a multi-part construction,as is typical in reusable pulse oximeter sensors, it may be difficult toperform such a quick and/or routine cleaning. For example, such athorough cleaning may require disassembly of the sensor and individualcleaning of the disassembled parts or may require careful cleaning usingutensils capable of reaching into cavities or crevices of the sensor.Such cleaning is labor intensive and may be impractical in a typicalhospital or clinic environment.

SUMMARY

Certain aspects commensurate in scope with the originally claimedinvention are set forth below. It should be understood that theseaspects are presented merely to provide the reader with a brief summaryof certain forms the invention might take and that these aspects are notintended to limit the scope of the invention. Indeed, the invention mayencompass a variety of aspects that may not be set forth below.

There is provided a sensor assembly that includes: a frame comprisingtwo or more structural supports; a coating provided over the frame,wherein the coating comprises at least one deformable region disposedbetween the two or more structural supports; at least one opticalcomponent disposed within the at least one deformable region, such thatthe at least one optical component can move relative to the two or morestructural supports; and a biasing component attached to an end of theframe such that at least two different portions of the coated frame arebiased closed in the absence of a sufficient opening force.

There is also provided a skeletal frame of a sensor that includes: twoor more structural support members having one or more spaces between thetwo or more structural support members, wherein the two or morestructural support members are configured to provide support to anoverlying coating when present.

There is also provided a method for manufacturing a skeletal frameworkof a sensor that includes: forming two or more structural supportmembers of a skeletal frame of a sensor having one or more spacesbetween the two or more structural support members, wherein the two ormore structural support members are configured to provide support to anoverlying coating when present.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the invention may become apparent upon reading thefollowing detailed description and upon reference to the drawings inwhich:

FIG. 1 illustrates a patient monitoring system coupled to amulti-parameter patient monitor and a sensor, in accordance with aspectsof the present technique;

FIG. 2 illustrates a perspective view of an internal frame for use in apatient sensor, in accordance with aspects of the present technique;

FIG. 3 illustrates a perspective view of the internal frame of FIG. 2 ina closed configuration, in accordance with aspects of the presenttechnique;

FIG. 4A illustrates a side view of the internal frame of FIG. 3;

FIG. 4B illustrates a flat spring for use with the internal frame ofFIGS. 2-4A, in accordance with aspects of the present technique;

FIG. 5A illustrates a side view of another internal frame for use in apatient sensor, in accordance with aspects of the present technique;

FIG. 5B illustrates a torsion spring for use with the internal frame ofFIG. 5A, in accordance with aspects of the present technique;

FIG. 6 illustrates a perspective view of an overmolded patient sensor,in accordance with aspects of the present technique;

FIG. 7 illustrates the overmolded patient sensor of FIG. 6 in use on apatient's finger, in accordance with aspects of the present technique;

FIG. 8 illustrates a cross-section taken along section line 8-8 of theovermolded patient sensor depicted in FIG. 6; and

FIG. 9 illustrates a cross-section taken along section line 9-9 of theovermolded patient sensor depicted in FIG. 6.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. In an effort to provide a concise description of theseembodiments, not all features of an actual implementation are describedin the specification. It should be appreciated that in the developmentof any such actual implementation, as in any engineering or designproject, numerous implementation-specific decisions must be made toachieve the developers' specific goals, such as compliance withsystem-related and business-related constraints, which may vary from oneimplementation to another. Moreover, it should be appreciated that sucha development effort might be complex and time consuming, but wouldnevertheless be a routine undertaking of design, fabrication, andmanufacture for those of ordinary skill having the benefit of thisdisclosure.

It is desirable to provide a comfortable and conformable reusablepatient sensor, such as for use in pulse oximetry or other applicationsutilizing spectrophotometry, that is easily cleaned and that isresistant to environmental light infiltration. In accordance with someaspects of the present technique, a reusable patient sensor is providedthat is overmolded to provide patient comfort and a suitably conformablefit. The overmold material provides a seal against bodily fluids, aswell as water or other cleaning fluids, that allows easy cleaningwithout disassembly or special tools. In accordance with some aspects ofthe present technique, the reusable patient sensor includes a mechanismproviding a biasing force, such as a metal flat spring or a torsionspring, to facilitate the secure placement of the sensor on a patient.

Prior to discussing such exemplary sensors in detail, it should beappreciated that such sensors are typically designed for use with apatient monitoring system. For example, referring now to FIG. 1, asensor 10 according to the present invention may be used in conjunctionwith a patient monitor 12. In the depicted embodiment, a cable 14connects the sensor 10 to the patient monitor 12. As will be appreciatedby those of ordinary skill in the art, the sensor 10 and/or the cable 14may include or incorporate one or more integrated circuit devices orelectrical devices, such as a memory, processor chip, or resistor, thatmay facilitate or enhance communication between the sensor 10 and thepatient monitor 12. Likewise the cable 14 may be an adaptor cable, withor without an integrated circuit or electrical device, for facilitatingcommunication between the sensor 10 and various types of monitors,including older or newer versions of the patient monitor 12 or otherphysiological monitors. In other embodiments, the sensor 10 and thepatient monitor 12 may communicate via wireless means, such as usingradio, infrared, or optical signals. In such embodiments, a transmissiondevice (not shown) may be connected to the sensor 10 to facilitatewireless transmission between the sensor 10 and the patient monitor 12.As will be appreciated by those of ordinary skill in the art, the cable14 (or corresponding wireless transmissions) are typically used totransmit control or timing signals from the monitor 12 to the sensor 10and/or to transmit acquired data from the sensor 10 to the monitor 12.In some embodiments, however, the cable 14 may be an optical fiber thatallows optical signals to be conducted between the monitor 12 and thesensor 10.

In one embodiment, the patient monitor 12 may be a suitable pulseoximeter, such as those available from Nellcor Puritan Bennett Inc. Inother embodiments, the patient monitor 12 may be a monitor suitable formeasuring tissue water fractions, or other body fluid related metrics,using spectrophotometric or other techniques. Furthermore, the monitor12 may be a multi-purpose monitor suitable for performing pulse oximetryand measurement of tissue water fraction, or other combinations ofphysiological and/or biochemical monitoring processes, using dataacquired via the sensor 10. Furthermore, to upgrade conventionalmonitoring functions provided by the monitor 12 to provide additionalfunctions, the patient monitor 12 may be coupled to a multi-parameterpatient monitor 16 via a cable 18 connected to a sensor input portand/or via a cable 20 connected to a digital communication port.

The sensor 10, in the example depicted in FIG. 1, is a clip-style sensorthat is overmolded to provide a unitary or enclosed assembly. The sensor10 includes an emitter 22 and a detector 24 which may be of any suitabletype. For example, the emitter 22 may be one or more light emittingdiodes adapted to transmit one or more wavelengths of light, such as inthe red to infrared range, and the detector 24 may be a photodetector,such as a silicon photodiode package, selected to receive light in therange emitted from the emitter 22. In the depicted embodiment, thesensor 10 is coupled to a cable 14 that is responsible for transmittingelectrical and/or optical signals to and from the emitter 22 anddetector 24 of the sensor 10. The cable 14 may be permanently coupled tothe sensor 10, or it may be removably coupled to the sensor 10—thelatter alternative being more useful and cost efficient in situationswhere the sensor 10 is disposable.

The sensor 10 described above is generally configured for use as a“transmission type” sensor for use in spectrophotometric applications,though in some embodiments it may instead be configured for use as a“reflectance type sensor.” Transmission type sensors include an emitterand detector that are typically placed on opposing sides of the sensorsite. If the sensor site is a fingertip, for example, the sensor 10 ispositioned over the patient's fingertip such that the emitter anddetector lie on either side of the patient's nail bed. For example, thesensor 10 is positioned so that the emitter is located on the patient'sfingernail and the detector is located opposite the emitter on thepatient's finger pad. During operation, the emitter shines one or morewavelengths of light through the patient's fingertip, or other tissue,and the light received by the detector is processed to determine variousphysiological characteristics of the patient.

Reflectance type sensors generally operate under the same generalprinciples as transmittance type sensors. However, reflectance typesensors include an emitter and detector that are typically placed on thesame side of the sensor site. For example, a reflectance type sensor maybe placed on a patient's fingertip such that the emitter and detectorare positioned side-by-side. Reflectance type sensors detect lightphotons that are scattered back to the detector.

For pulse oximetry applications using either transmission or reflectancetype sensors the oxygen saturation of the patient's arterial blood maybe determined using two or more wavelengths of light, most commonly redand near infrared wavelengths. Similarly, in other applications a tissuewater fraction (or other body fluid related metric) or a concentrationof one or more biochemical components in an aqueous environment may bemeasured using two or more wavelengths of light, most commonly nearinfrared wavelengths between about 1,000 nm to about 2,500 nm. It shouldbe understood that, as used herein, the term “light” may refer to one ormore of infrared, visible, ultraviolet, or even X-ray electromagneticradiation, and may also include any wavelength within the infrared,visible, ultraviolet, or X-ray spectra.

Pulse oximetry and other spectrophotometric sensors, whethertransmission-type or reflectance-type, are typically placed on a patientin a location conducive to measurement of the desired physiologicalparameters. For example, pulse oximetry sensors are typically placed ona patient in a location that is normally perfused with arterial blood tofacilitate measurement of the desired blood characteristics, such asarterial oxygen saturation measurement (SaO₂). Common pulse oximetrysensor sites include a patient's fingertips, toes, forehead, orearlobes. Regardless of the placement of the sensor 10, the reliabilityof the pulse oximetry measurement is related to the accurate detectionof transmitted light that has passed through the perfused tissue and hasnot been inappropriately supplemented by outside light sources ormodulated by subdermal anatomic structures. Such inappropriatesupplementation and/or modulation of the light transmitted by the sensorcan cause variability in the resulting pulse oximetry measurements.

As noted above, the overmolded sensor 10 discussed herein may beconfigured for either transmission or reflectance type sensing. Forsimplicity, the exemplary embodiment of the sensor 10 described hereinis adapted for use as a transmission-type sensor. As will be appreciatedby those of ordinary skill in the art, however, such discussion ismerely exemplary and is not intended to limit the scope of the presenttechnique.

Referring now to FIG. 2, an internal frame 26 for a sensor 10 isdepicted. In the depicted example, the internal frame 26 is a skeletalframe for the sensor 10. Such a skeletal frame may include differentstructures or regions that may or may not have similar rigidities. Forexample, the depicted skeletal frame includes structural supports 28that define the general shape of the sensor 10 when coated, as discussedbelow with regard to FIGS. 6-9. In view of their structure providingfunction, the structural supports 28 may be constructed to besubstantially rigid or semi-rigid. In addition, the skeletal frame mayinclude a cable guide 32 through which a cable, such as an electrical oroptical cable, may pass to connect to the electrical or opticalconductors attached to the emitter 22 and/or detector 24 upon assembly.Likewise, a skeletal frame, such as the depicted internal frame 26, mayinclude component housings, such as the emitter housing 38 and detectorhousing 40 and struts 42 attaching such housings to the remainder of theskeletal frame. The struts 42 may be relatively flexible, allowing theemitter housing 38 and/or the detector housing 40 to move vertically(such as along an optical axis between the respective housings) relativeto the structural supports 28 of the skeletal frame. Alternatively, inembodiments where the struts 42 are relatively rigid, where multiplestruts 42 are employed to attach the housings 38 and 40 to thestructural supports 28, or where the internal frame is substantiallysolid instead of skeletal, the housings 38 and/or 40 may be fixedrelative to the respective structural supports 28 and, therefore, movewith the structural supports 28.

In embodiments where the internal frame 26 is skeletal, the variousstructural supports 28, housings 38 and 40, struts 42, and otherstructures may define various openings and spaces between and/or aroundthe structures of the skeletal frame. In this manner, the skeletal frameprovides structural support at specific locations for a coating orovermolding. However, in regions where structural support is notprovided, flexibility and freedom of motion in an overlying coating orovermolding may be possible. For example, in one implementation, theemitter housing 38 and/or the detector housing 40 may be attached to theremainder of the skeletal frame by flexible struts 42, as depicted inFIGS. 2-4. In such implementations, a coating provided proximate to theemitter housing 38 and/or detector housing 40 may be sufficientlyflexible (such as due to the elasticity and/or the thinness of thecoating material in the open areas of the skeletal frame) such that thehousings 38 and 40 may move independent of the structural supports 28 ofthe frame 26 along an optical axis between the housings 38 and 40.

In certain embodiments, the internal frame 26 is constructed, in wholeor in part, from polymeric materials, such as thermoplastics, capable ofproviding a suitable rigidity or semi-rigidity for the differentportions of the internal frame 26. Examples of such suitable materialsinclude polypropylene and nylon, though other polymeric materials mayalso be suitable. For example, in one embodiment, the internal frame 26is constructed from polyurethane having a durometer of 65 Shore D. Inother embodiments, the internal frame 26 is constructed, in whole or inpart, from other suitably rigid or semi-rigid materials, such asstainless steel, aluminum, magnesium, graphite, fiberglass, or othermetals, alloys, or compositions that are sufficiently ductile and/orstrong. For example, metals, alloys, or compositions that are suitablefor diecasting, sintering, lost wax casting, stamping and forming, andother metal or composition fabrication processes may be used toconstruct the internal frame 26.

In addition, the internal frame 26 may be constructed as an integralstructure or as a composite structure. For example, in one embodiment,the internal frame 26 may be constructed as a single piece from a singlematerial or from different materials. Alternatively, the internal frame26 may be constructed or assembled from two or more parts that areseparately formed. In such embodiments, the different parts may beformed from the same or different materials. For example, inimplementations where different parts are formed from differentmaterials, each part may be constructed from a material having suitablemechanical and/or chemical properties for that part. The different partsmay then be joined or fitted together to form the internal frame 26.

In addition, the internal frame 26 may be molded, formed, or constructedin a different configuration than the final sensor configuration. Forexample, referring now to FIG. 2, the internal frame 26 for use in thesensor 10 may be initially formed in a generally open, or flat,configuration compared to the relatively closed configuration of theinternal frame 26 when folded to form the sensor 10. In suchembodiments, a top portion 46 and a bottom portion 48 of the frame 26may be formed in a generally open or planar configuration in which thetwo portions 46 and 48 are connected by a connective portion 50.

For example, the top portion 46, bottom portion 48, and connectiveportion 50 may be molded or formed as a single piece in an openconfiguration. In such an embodiment, the connective portion 50 may bebroken or deformed to bring the top portion 46 and bottom portion 48into a closed configuration, as depicted in FIGS. 3, 4A, and 5A. In thisimplementation, the top portion 46 and bottom portion 48 may be securedtogether, such as via a snap fitting process, ultrasonic welding, orheat staking or by application of an adhesive or mechanical fastener.

Alternatively, the internal frame 26 may be formed as multiple partsthat are joined together to form the internal frame 26. For example, thetop portion 46, bottom portion 48, tabs 52 and/or the connective portion50 may be molded or formed separately and subsequently secured togetherto form the internal frame 26. The different parts of the internal frame26 may be joined together using one or more of the techniques notedabove, such as a snap fitting process, ultrasonic welding, or heatstaking or by application of an adhesive or mechanical fastener. If theinternal frame 26 is secured together in an open configuration, theconnective portion 50 may be broken or deformed to bring the top portion46 and bottom portion 48 into a closed configuration, as depicted inFIGS. 3 4A, and 5A. Alternatively, the internal frame 26 may beconstructed in a closed configuration from the separately molded orformed parts, such as the top portion 46, bottom portion 48, and/or tabs52.

In certain embodiments, the internal frame 26 is fitted with a spring orother biasing component, such as a formed flat spring 58 (as depicted inFIGS. 3, 4A, and 4B) or a torsion spring 60 (as depicted in FIGS. 5A and5B). As will be appreciated by those of ordinary skill in the art, suchbiasing components may include elastic bodies or devices that may bedistorted and that recover their original shape when released afterbeing distorted. Similarly, a component or material that can storeenergy and release the energy to provide a gripping force, as describedherein, may function as a spring or biasing component. For example, anovermolding material or composition, as discussed with regard to FIGS.6-9, may have sufficient elasticity to function as a biasing componentas discussed herein, with or without the additional gripping forceprovided by a component such as the flat spring 58 or the torsion spring60. For the purpose of this example, however, the sensor 10 is providedwith and discussed as including a flat spring 58 (in FIGS. 3 and 4A) ora torsion spring 60 (in FIG. 5A).

Referring to FIGS. 3 and 4A, a flat spring 58 is fitted at or near theend of the internal frame 26 that is opposite from where the finger,toe, or other patient appendage is inserted into the assembled sensor.In alternative embodiments, the flat spring 58 connects two differentportions or halves of the internal frame 26 to form the internal frame26. In the depicted embodiment, slots 64 are provided in the internalframe 26 that are engaged by complementary spring tabs 66 to fit theflat spring 58 to the internal frame 26. For example, in an embodimentin which the internal frame 26 is molded or formed as a relatively open,single-piece, as depicted in FIG. 2, the internal frame 26 may be bentfrom the relatively open configuration to a closed configuration, asdepicted in FIGS. 3 and 4A. The flat spring 58 may be fitted or attachedto the internal frame 26 when in the closed configuration to provide abiasing force that maintains the internal frame 26 in the closedconfiguration. Referring now to FIG. 5A, the torsion spring 60 may besimilarly fitted or attached to the internal frame 26 when in the closedconfiguration to provide a biasing force that maintains the internalframe 26 in the closed configuration.

The flat spring 58 or torsion spring 60 may be constructed from avariety of materials or combinations of materials that provide thedesired resiliency and clamping force. For example, in certainembodiments, the flat spring 58 or torsion spring 60 may be constructedfrom a metal alloy, such as stainless steel. In one such stainless steelflat spring embodiment, the flat spring 58 may be made from 301 highyield stainless steel that is 0.010 inch thick and that producesapproximately 1.25 pounds of force at the optic plane (that is a planethrough the emitter 22 and detector 24) with a finger pad separation ofapproximately 15 mm. In other embodiments, the flat spring 58 or torsionspring 60 may be constructed from materials such as plastics, polymers,composites, and so forth that provide the desired resilience andelasticity.

An overmolded sensor 10 (as discussed with regard to FIGS. 6-9)incorporating a flat spring 58, a torsion spring 60, or other biasingcomponent, disposed on the internal frame 26 may be opened for placementon a patient's finger, toe, ear, or other appendage by applying a forceto separate the top portion 46 and bottom portion 48 of the internalframe 26. For example, the flat spring 58 (in FIGS. 3 and 4A) or thetorsion spring 60 (in FIG. 5A) provide or contribute to a closing forcebiasing the top portion 46 and the bottom portion 48 of the frame 26together. An opposing force, however, may be applied to force the topportion 46 and bottom portion 48 apart. In the example depicted, anopposing force may be applied to projections, such as tabs 52, providedat the end of the internal frame 26 to which the flat spring 58 ortorsion spring 60 is fitted such that the force provided by therespective spring is overcome. In this manner, the tabs 52 are movedtoward one another while the top portion 46 and bottom portion 48 aremoved apart from one another.

As noted above, in certain embodiments of the present technique, theframe 26 (such as a skeletal internal frame) is coated to form a unitaryor integral sensor assembly, as depicted in FIGS. 6-9. Such overmoldedembodiments may result in a sensor assembly in which the internal frame26 is completely or substantially coated. In embodiments in which theinternal frame 26 is formed or molded as a relatively open or flatstructure, the overmolding or coating process may be performed prior toor subsequent to bending the internal frame 26 into the closedconfiguration.

For example, the sensor 10 may be formed by an injection moldingprocess. In one example of such a process the internal frame 26 may bepositioned within a die or mold of the desired shape for the sensor 10.A molten or otherwise unset overmold material may then be injected intothe die or mold. For example, in one implementation, a moltenthermoplastic elastomer at between about 400° F. to about 450° F. isinjected into the mold. The overmold material may then be set, such asby cooling for one or more minutes or by chemical treatment, to form thesensor body 5 about the internal frame 26. In certain embodiments, othersensor components, such as the emitter 22 and/or detector 24, may beattached or inserted into their respective housings or positions on theovermolded sensor body.

Alternatively, the optical components (such as emitter 22 and detector24) and/or conductive structures (such as wires or flex circuits) may beplaced on the internal frame 26 prior to overmolding. The internal frame26 and associated components may then be positioned within a die or moldand overmolded, as previously described. To protect the emitter 22,detector 24, and or other electrical components, conventional techniquesfor protecting such components from excessive temperatures may beemployed. For example, the emitter 22 and/or the detector 24 may includean associated clear window, such as a plastic or crystal window, incontact with the mold to prevent coating from being applied over thewindow. In one embodiment, the material in contact with such windows maybe composed of a material, such as beryllium copper, which prevents theheat of the injection molding process from being conveyed through thewindow to the optical components. For example, in one embodiment, aberyllium copper material initially at about 40° F. is contacted withthe windows associated with the emitter 22 and/or detector 24 to preventcoating of the windows and heat transfer to the respective opticalcomponents. As will be appreciated by those of ordinary skill in theart, the injection molding process described herein is merely onetechnique by which the frame 26 may be coated to form a sensor body,with or without associated sensing components. Other techniques whichmay be employed include, but are not limited to, dipping the frame 26into a molten or otherwise unset coating material to coat the frame 26or spraying the frame 26 with a molten or otherwise unset coatingmaterial to coat the frame 26. In such implementations, the coatingmaterial may be subsequently set, such as by cooling or chemical means,to form the coating. Such alternative techniques, to the extent thatthey may involve high temperatures, may include thermally protectingwhatever optical components are present, such as by using berylliumcopper or other suitable materials to prevent heat transfer through thewindows associated with the optical components, as discussed above.

By such techniques, the frame 26, as well as the optical components andassociated circuitry where desired, may be encased in a coating material68 to form an integral or unitary assembly with no exposed or externalmoving parts of the internal frame 26. For example, as depicted in FIG.6, the sensor 10 includes features of the underlying internal frame 26that are now completely or partially overmolded, such as the overmoldedexternal cable guide 70, tabs 72, emitter housing 74, and detectorhousing 76. In addition, the overmolded sensor 10 includes an overmoldedupper portion 78 and lower portion 80 that may be fitted to the finger82 of a patient (as depicted in FIG. 7), or to the toe, ear, or otherappendage of the patient, as appropriate.

In one implementation, the overmolding or coating 68 is a thermoplasticelastomer or other conformable coating or material. In such embodiments,the thermoplastic elastomer may include compositions such asthermoplastic polyolefins, thermoplastic vulcanizate alloys, silicone,thermoplastic polyurethane, and so forth. In one embodiment, theovermolding material is polyurethane having a durometer of 15 Shore A.As will be appreciated by those of ordinary skill in the art, theovermolding composition may vary, depending on the varying degrees ofconformability, durability, wettability, or other physical and/orchemical traits that are desired. Furthermore, the coating material 68may be selected to provide additional spring force to that provided bythe biasing component (such as flat spring 58 or torsion spring 60).

Furthermore, the coating material 68 may be selected based upon thedesirability of a chemical bond between the internal frame 26 and thecoating material 68. Such a chemical bond may be desirable fordurability of the resulting overmolded sensor 10. For example, toprevent separation of the coating 68 from the internal frame 26, thematerial used to form the coating 68 may be selected such that thecoating 68 bonds with some or all of the internal frame 26 during theovermolding process. In such embodiments, the coating 68 and theportions of the internal frame 26 to which the coating 68 is bonded arenot separable, i.e., they form one continuous and generally inseparablestructure.

Furthermore, in embodiments in which the coating 68 employed is liquidor fluid tight, such a sensor 10 may be easily maintained, cleaned,and/or disinfected by immersing the sensor into a disinfectant orcleaning solution or by rinsing the sensor 10 off, such as under runningwater. In particular, such an overmolded sensor assembly may begenerally or substantially free of crevices, gaps, junctions or othersurface irregularities typically associated with a multi-partconstruction which may normally allow the accumulation of biologicaldetritus or residue. Such an absence of crevices and otherirregularities may further facilitate the cleaning and care of thesensor 10.

Turning now to FIGS. 8 and 9, cross-sections of the coated sensorassembly 10 are depicted taken through transverse optical planes,represented by section line 8 and 9 of FIG. 6 respectively. FIGS. 8 and9 depict, among other aspects of the sensor 10, the overmolding material68 as well as underlying portions of the internal frame 26, such as theemitter housing 38 and detector housing 40, along with the respectiveemitter 22, detector 24, and signal transmission structures (such aswiring 83 or other structures for conducting electrical or opticalsignals). In the depicted embodiment, the emitter 22 and detector 24 areprovided substantially flush with the patient facing surfaces of thesensor 10, as may be suitable for pulse oximetry applications. For otherphysiological monitoring applications, such as applications measuringtissue water fraction or other body fluid related metrics, otherconfigurations may be desirable. For example, in such fluid measurementapplications it may be desirable to provide one or both of the emitter22 and detector 24 recessed relative to the patient facing surfaces ofthe sensor 10. Such modifications may be accomplished by properconfiguration or design of a mold or die used in overmolding theinternal frame 26 and/or by proper design of the emitter housing 38 ordetector housing 40 of the internal frame 26.

In addition, as depicted in FIGS. 8 and 9, in certain embodimentsportions 84 of the coating material 68 may be flexible, such as thin ormembranous regions of coating material 68 disposed between structuralsupports 28 of a skeletal frame. Such flexible regions 84 allow agreater range of digit sizes to be accommodated for a given retention orclamping force of the sensor 10. For example, the flexible regions 84may allow the emitter 22 and/or detector 24, to flex or expand apartfrom one another along the optical axis in embodiments in which therespective housings 38 and 40 are flexibly attached to the remainder ofthe frame 26. In this manner, the sensor 10 may accommodate differentlysized digits. For instance, for a relatively small digit, the flexibleregion 84 may not be substantially deformed or vertically displaced, andtherefore the emitter 22 and/or detector 24 are not substantiallydisplaced either. For larger digits, however, the flexible regions 84may be deformed or displaced to a greater extent to accommodate thedigit, thereby displacing the emitter 22 and/or detector 24 as well. Inaddition, for medium to large digits, the flexible regions 84 may alsoincrease retention of the sensor 10 on the digit by increasing thesurface area to which the retaining force is applied.

Furthermore, as the flexible regions 84 deform, the force applied to thedigit is spread out over a large area on the digit due to thedeformation of the flexible region 84. In this way, a lower pressure ondigits of all sizes may be provided for a given vertical force.Therefore, a suitable conforming fit may be obtained in which theemitter 22 and detector 24 are maintained in contact with the digitwithout the application of concentrated and/or undesirable amounts offorce, thereby improving blood flow through the digit.

In the example depicted in FIGS. 6-9, flaps or side extensions 88 of thecoating material 68 on the sides of the sensor 10 are depicted whichfacilitate the exclusion of environmental or ambient light from theinterior of the sensor 10. Such extensions help prevent or reduce thedetection of light from the outside environment, which may beinappropriately detected by the sensor 10 as correlating to the SaO₂.Thus, a pulse oximetry sensor may detect differences in signalmodulations unrelated to the underlying SaO₂ level. In turn, this mayimpact the detected red-to-infrared modulation ratio and, consequently,the measured blood oxygen saturation (SpO₂) value. The conformability ofthe fit of sensor 10 and the use of side extensions 88, therefore, mayhelp prevent or reduce such errors.

While the exemplary medical sensors 10 discussed herein are someexamples of overmolded or coated medical devices, other such devices arealso contemplated and fall within the scope of the present disclosure.For example, other medical sensors and/or contacts applied externally toa patient may be advantageously applied using an overmolded sensor bodyas discussed herein. Examples of such sensors or contacts may includeglucose monitors or other sensors or contacts that are generally heldadjacent to the skin of a patient such that a conformable andcomfortable fit is desired. Similarly, and as noted above, devices formeasuring tissue water fraction or other body fluid related metrics mayutilize a sensor as described herein. Likewise, other spectrophotometricapplications where a probe is attached to a patient may utilize a sensoras described herein.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims. Indeed, the present techniques may not only be appliedto transmission type sensors for use in pulse oximetry, but also toretroflective and other sensor designs as well. Likewise, the presenttechniques are not limited to use on fingers and toes but may also beapplied to placement on other body parts such as in embodimentsconfigured for use on the ears or nose.

1. A sensor assembly, comprising: a frame comprising two or morestructural supports; a coating provided over the frame, wherein thecoating comprises at least one deformable region disposed between thetwo or more structural supports; at least one optical component disposedwithin the at least one deformable region, such that the at least oneoptical component can move relative to the two or more structuralsupports; and a biasing component attached to an end of the frame suchthat at least two different portions of the coated frame are biasedclosed in the absence of a sufficient opening force.
 2. The sensorassembly of claim 1, wherein the at least one optical componentcomprises at least one of a light emitting diode or a photodetector. 3.The sensor assembly of claim 1, wherein the coating comprises a firstdeformable region disposed between first and second structural supportsand a second deformable region disposed between third and fourthstructural supports.
 4. The sensor assembly of claim 3, wherein the atleast one optical component comprises a light emitting diode disposedwithin the first deformable region and capable of moving relative to thefirst and second structural supports and a photodetector disposed withinthe second deformable region and capable of moving relative to the thirdand fourth structural supports.
 5. The sensor assembly of claim 1,comprising one or more signal transmission structures connected to theat least optical component.
 6. The sensor assembly of claim 1, whereinthe sensor assembly comprises at least one of a pulse oximetry sensor, asensor for measuring a water fraction, or a combination thereof.
 7. Thesensor assembly of claim 1, wherein the frame comprises a single moldedpart.
 8. The sensor assembly of claim 1, wherein the frame comprises twoor more parts joined to form the frame.
 9. The sensor assembly of claim1, wherein the coating comprises a thermoplastic elastomer.
 10. Thesensor assembly of claim 9, wherein the thermoplastic elastomercomprises at least one of a thermoplastic polyolefin, a thermoplasticvulcanizate alloy, thermoplastic polyurethane, silicone, or acombination thereof.
 11. The sensor assembly of claim 1, wherein thecoating comprises a conformable material.
 12. The sensor assembly ofclaim 1, wherein no moving parts of the frame remain exposed from thecoating.
 13. The sensor assembly of claim 1, wherein the sensor assemblyis fluid tight.
 14. The sensor assembly of claim 1, wherein the coatingis chemically bonded to the frame.
 15. The sensor assembly of claim 1,comprising a pulse oximeter monitor configured to receive data from theat least one optical component.
 16. The sensor assembly of claim 1,comprising a multi-parameter monitor configured to receive data from theat least one optical component.
 17. The sensor assembly of claim 1,comprising at least one integrated circuit device.
 18. The sensorassembly of claim 1, comprising a cable comprising one or moreintegrated circuits.
 19. The sensor assembly of claim 1, comprising anadapter cable connected to one or more signal transmission structures ofthe sensor assembly.
 20. The sensor assembly of claim 1, wherein thebiasing component comprises at least one of a formed flat spring or atorsion spring.
 21. The sensor assembly of claim 1, wherein the biasingcomponent comprises a metal alloy.
 22. The sensor assembly of claim 1,wherein the biasing component comprises a polymeric material.
 23. Askeletal frame of a sensor, comprising: two or more structural supportmembers having one or more spaces between the two or more structuralsupport members, wherein the two or more structural support members areconfigured to provide support to an overlying coating when present. 24.The skeletal frame of claim 23, wherein the two or more structuralsupport members comprise at least one of an emitter housing or adetector housing.
 25. The skeletal frame of claim 23, wherein the two ormore structural support members form a first portion and a secondportion configured to move relative to one another.
 26. The skeletalframe of claim 23, wherein the two or more structural support membersare formed as a single piece.
 27. The skeletal frame of claim 23,wherein the two or more structural support members are formed asseparate pieces and joined to form the skeletal frame.
 28. The skeletalframe of claim 23, comprising a biasing component attached to the two ormore structural support members.
 29. The skeletal frame of claim 23,wherein the two or more structural support members comprise a rigidmaterial.
 30. The skeletal frame of claim 23, wherein the two or morestructural support members comprise at least one of a metal, a metallicalloy, a thermoplastic material, or a composite material.
 31. A methodfor manufacturing a skeletal framework of a sensor, comprising: formingtwo or more structural support members of a skeletal frame of a sensorhaving one or more spaces between the two or more structural supportmembers, wherein the two or more structural support members areconfigured to provide support to an overlying coating when present. 32.The method of claim 31, wherein forming the two or more structuralsupport members comprises performing at least one of a moldingoperation, a diecasting operation, a sintering operation, a castingoperation, or a stamping operation.
 33. The method of claim 31, whereinforming the two or more structural support members comprises forming thetwo or more structural support members as a single piece.
 34. The methodof claim 31, wherein forming the two or more structural support memberscomprises forming the two or more structural support members as aplurality of pieces and joining the plurality of pieces to form theskeletal frame.
 35. The method of claim 34, wherein some or all of theplurality of pieces are formed from different materials.
 36. The methodof claim 31, wherein the two or more structural support memberscomprises one or more of a thermoplastic material, a metal, a metallicalloy, or a composite material.